A color filter used for a color image pick-up device which finds a big demand for a VTR camera and a color copying machine, and for a liquid crystal color display device replacing for a CRT system because of a tendency to be lighter and thinner, is formed by providing minute areas colored with at least two kinds of hue, on a solid image pick-up device or a transparent substrate.
So far, such a colored thin film has been prepared by dyeing or printing method, and when an espcially high definition image is required, the dyeing method has mainly been used.
However, a color filter by the dyeing method is usually manufactured by forming in advance an image on a substrate with a dyeable base material, such as, a natural photosensitive resin, for instance gelatine, an amine modified polyvinyl alcohol, an amine modified acrylic resin, or the like, followed by dyeing with a dye such as an acid dye, etc. and, since it is necessary to form multiple colors on the same substrate, a protection process against dyeing must be done every time the color is changed, and this invites a problem that the process is very complex and long. Further, as light resistance, heat resistance and moisture resistance of dyes and resins used are generally low, color filters prepared therewith also have relatively unreliable light, heat and moisture resistance.
A color filter by the printing method is manufactured by printing with an ink which is prepared by dispersing a pigment in a thermo- or photosetting resin, and then curing the resin by heat or light. However, with this color filter, a high definition image is difficult to form and the image obtained has a problem in its surface smoothness. In order to make the process simpler, a method to disperse or dissolve coloring matters in the resin in advance has been proposed.
For example, Japanese Patent Application Laid-open (Kokai) Nos. 1-152449; 1-254918; 2-153353 and 2-804 propose methods for forming a multicolor pattern by dispersing pigments in a photosensitive resin containing a multifunctional acrylate monomer and a highly sensitive halomethyl-s-triazine photopolymerization initiator. These processes are simpler than the formation of a color filter by the dyeing method. As the resins and pigments used have high heat and light resistance, the filters manufactured by these processes are generally more reliable than the filters made by the dyeing method. However, since radicals generated from the photopolymerization initiator during photopolymerization are trapped by oxygen, those photosensitive resin materials cannot be cured sufficiently under the condition exposed to air. As the result, after the photopolymerizable composition is coated and dried, it is necessary to form a film (an oxygen blocking film) of PVA, etc. further on the coated composition to block oxygen. Accordingly, there remains some troubles in view of simplifying the process.
On the other hand, Japanese Patent Application Laid-open (Kokai) Nos. 60-129738 and 60-129739 propose a method in which the oxygen film is not required. This method employs a coloring composition using a photosensitive PVA-stilbazolium cross-linking resin. However, since the base resin is PVA which has low heat resistance and is water soluble, there remains a problem of its moisture resistance. Further, as the boiling point of water is low, it is disadvantageous to spin-coat the composition on a large size substrate.